![]() ![]() The number 5 is missing from row B and its only possible position is cell B3. Due to other 8s on the grid, the only place it can go is cell C2.īecause of the number 8 just placed, the only position in row B for another 8 is cell B4.īecause of the number 8 just placed, the only position in column 6 for another 8 is cell F6. The number 8 does not yet appear in column 2. The number 4 is missing from row B and its only possible position is cell B2. The remaining possibilities are marked with small numbers. Therefore 4 can be eliminated from other cells in column 3 including A3, B3. In box G1-I3, the missing 4 can only go in cell G3 or H3. Therefore 2 can be eliminated from other cells in row B including B3, B4. In box A7-C9, the missing 2 can only go in cell B7 or B8. Therefore 1 can be eliminated from other cells in row B including B2, B3, B4. In box A7-C9, the missing 1 can only go in cell B7 or B8. The number 5 is missing from box D7-F9 and its only possible position is cell D8. Due to other 8s on the grid, the only place it can go is cell D7. The number 8 does not yet appear in column 7. The number 4 is missing from row E and its only possible position is cell E4.īecause of the number 4 just placed, the only position in row F for another 4 is cell F7. The number 6 is missing from row E and its only possible position is cell E6.īecause of the number 6 just placed, the only position in row D for another 6 is cell D3.īecause of the number 6 just placed, the only position in column 1 for another 6 is cell B1.īecause of the number 6 just placed, the only position in row C for another 6 is cell C5. The number 7 is missing from box A7-C9 and its only possible position is cell C7. Due to other 9s on the grid, the only place it can go is cell H8. The number 9 does not yet appear in column 8. Due to other 3s on the grid, the only place it can go is cell H2. The number 3 does not yet appear in column 2. Due to other 6s on the grid, the only place it can go is cell I8. The number 6 does not yet appear in row I. Due to other 3s on the grid, the only place it can go is cell A9. The number 3 does not yet appear in row A. With our step-by-step solutions, you can be confident that your readers will enjoy solving your Sudokus with pencil and paper, and will never be frustrated by logical dead ends. Naturally each puzzle can be solved in many different ways, but every way leads to the same solution. ![]() The step-by-step shows one way to solve puzzle using only logical reasoning. Our puzzles never require "trial and error", which is easy for computers but tedious for people.Įvery Sudoku puzzle we provide comes with its step-by-step solution, such as the hard example shown below. The difficulty of a puzzle is determined by the depth of logic required. I find this mistake (saying the above A, B should be "locked pairs") in the book "Extreme Sudoku for Dummies" by Andrew Heron & Andrew Stuart, so I check here, I hope this helps the discussion to go clear.Example Sudoku - Hard Level - 27 Givens - Step-by-Step Solution - By Web SudokuĮvery Sudoku we create has a unique solution which can be reached by logic alone. As a result, (B5, E2) could be (C, non-C), (non-C), or (C, C), and in all scenarios, C should be eliminated from cell E5. Similarly, the two A's in cells B2 & E2 are not a "locked pair" either, there could be other A's in column 2. Note that: the two B's in cells B2 & B5 are not a "locked pair", in other words, there could be other B's in row B. The statement "So whatever happens, C is certain in one of those two cells marked C.", which implies C in one of the two cells, actually C can also be in both cells. The definition of "see" is "two cells within the same element (row, column, box)" (the two cells see each other) 1 to explain this.Ĭell B2 with AB (bi-value), the pivot, which connects (sees) B5 and E2Ĭell E5, the target cell to eliminate C, if any, which "sees" both B5 and E2 There's a small mistake about Y-wing in the logic of proof: ![]()
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